Production of solvents from refined pitch



July 28, 1942- J. E. HARVEY, JR 2,291,317

PRODUCTION OF SOLVENTS FROM REFINED4 FITCH Filed March 14, 1941 @Piagge/f www Patented July 28, 1942 PRODUCTION OF SOLVENTS FROM REFINED PITCH Jacquelin E. Harvey, Jr., Atlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Application March 14, 1941, Serial No. 383,467

6 Claims.

The present invention relates to the production of valuable liquids from tars and fractions thereof, crude and/or rened.

This application is a continuation in part of my application Serial No. 345,438, filed July 13, 1940, for Synthesis of valuable liquids, copending herewith, as to all matter common to the two applications.

An object of the present invention is the subjection of tars and fractions thereof, crude and/or refined, to the action of hydrogen in step-wise manner, whereby to provide solvents of increased solvency and boiling range.

A further object of the present invention is the production of solvents, the characteristics of which are, among other things, dependent upon hydrogen supply.

Other objects of the present invention will be apparent from the following disclosures.

Suitable starting materials of the present invention include tars and fractions thereof derived from coal and petroleum, as for instance coke-oven tar, gas house tar, water gas tar and tars of aromatic content derived from petroleum or fractions thereof; tars produced by cracking hydrocarbons; tars resulting from the action of hydrogen or hydrocarbons; tars resulting from catalytic action on hydrocarbons, including polymerization; high boiling aromatic extracts of carbonaceous substances; high boiling hydrocarbons of olefinic and naphthenic content; tars and fractions thereof of aromatic content.

Especially attractive as starting material is high temperature coke-oven tar which is available in large quantities at low price.

The present invention may be viewed broadly as providing a process for the production of solvents by subjecting the starting material, in stepwise manner, to the controlled action of hydrogen whereby to produce solvents of increased boiling range and enhanced solvency.

The following examples will serve to illustrate the general principles upon which the practice of the present invention is based, as well as the process of the present invention.

The invention will be understood from the following description of illustrative steps comprising various methods of securing the objects of the invention, when read in connection with the accompanying drawing wherein the figure is a diagrammatic sketch of an apparatus for carrying out a form of the process ofv the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indicated by legend.

Exam-ple 1.-A coal tar boiling substantially 3% at 210 C. is passed through a high pressure reaction chamber at 400 C. and 200 atmospheres pressure. Catalyst is molybdenum sulfide. Time of contact is 1 hour. Gas flow is sufficient to provide a beneficiated tar having a lowered solvency, boiling range, specific gravity and viscosity. The thus beneciated tar is stripped to 315 C. and the distillate therefrom boiling:

Per cent I. B. P.-210 C 27.5 ZIO-235 C 14.0 235-270 C 34.0 2'70-315 C 24.5

The stripped material whose end point was substantially 315 C. is passed through a high pressure reaction vessel at 475 C. and a pressure of 250 atmospheres with flow of hydrogen so controlled as to provide a solvent, as compared to its intermediate parent material, having increased boiling range, and solvency.

Example 2.-A residue from coal tar boiling substantially 31% at 380o C., Conradson carbon 14.5 and specic gravity 1,1208 was passed through a high pressure reaction chamber at 410 C. and 300 atmospheres pressure; time of contact 1 hour. Catalyst is cobalt sulfide. Gas oW sufiicient to provide a beneciated tar fraction having a specific gravity of 1.0625, a Conradson carbon of 4.89 and lower solvency than the starting product. The thus beneciated tar fraction was stripped to 350 C., the distillate therefrom boiling:

Per cent I. B. P.-210 C 4.6 210-235 C 0.4 235-2'70 C 4.0 270-315 C 34.0 315-350 C 57.0

The stripped material whose end point Was substantially 350 C. was passed through a high pressure reactor at 465 C. and 300 atmospheres pressure, while contacting a molybdenum-tin sulfide catalyst. Flow of hydrogen so controlled as to induce a solvent having, as compared to the intermediate starting material, an increased boiling range and solvency.

The solvents so produced may be fractionated to provide solvents and plasticizers of any boiling range, as for instance:

C. Benzol 'T8-120 Toluol 100-150 Hi-ash naphtha 150-200 Heavy naphtha 150-290 Plasticizers 160-360 The solvents of the present invention serve as good substitutes for the commercial solvents noted.

It has been discovered that when subjecting certain mixtures of refined coal tar fractions to Y the action of hydrogen in accordance with the present process for the production of solvents and/or plasticizers that the formerly accepted teaching that product increment, depolymerization and/or hydrogen absorption are linear func- One of the preferred starting materials of theV present process is a mixture of refined coal tar fractions boiling predominantly above 355 or 380 C. Such a starting material is conveniently the nal residue resulting from evaporating coal tar toY dryness or substantial dryness andthen stripping wood preservative from the distillate. This final residue mass of refined coal tar fractions is an especially suitable refined coal tar pitch to be used as starting material of the present process. However, in contradistinction to the mixture of crude coal tar fractions boiling predominantly above 250 or 300 C., whenY the aforenamed preferred starting material is subjected to the action of hydrogen for production of solvents and/or plasticizers, the newly induced fractions, depolymerization and/or hydrogen absorption are not, as described for the other mixture of crude coal tar fractions, linear functions of the time. A critical period of treatment by or with hydrogen exists, and which if exceeded causes loss of newly induce-d fractions, polymerization and/or lessened hydrogen absorption on certain fractions of the preferred starting material under treatment. y

'I'he critical time element because of the obvious possible variations in the characteristics of the aforenamed refined coal tar pitch cannot be spoken of as an arbitrary figure. It can be stated, however, that if the refined coal tar pitch` were to be subjected to the action of hydrogen for such a length of time, which for other crude coal tar fractions would illustrate that the newlyV induced fraction, depolymerization and/or hydrogen absorption were linear functions of the time element, loss of induced products, polymerization and/or lessening of hydrogen absorption would occur. When treating the refined pitch by or'with hydrogen,the critical time element is in the-order of about three hours. I-

In the disclosures made herein and in the appended claims distillate removal of low boiling portions from the beneficiated material is considered the equivalent of fractional removal by gas movement, solvent action or the like. The converse also obtains.

In accordance with the present process the refined coal tar pitch is passed through a high pressure reaction vessel while simultaneously fiowing hydrogen therewith; catalyst molybdenum sulfide and the time of contact less than three hours; hydrogen flow 15,000 cubic feet per barrel feed stock; total pressure 400 atmospheres.

The beneficiated material is characterized by lowered specific gravity, viscosity and coke residue, and the` high boiling fractions relatively susceptible to thermal degradation will, at

least to a degree, be rendered thermally stable. Too, the beneficiated material as flowing from the first hydrogen action will provide conformance to the accepted teaching that the newly induced fractions, Ydepolymerization and/or hydrogen absorption are linear functions of the time element, whereas if an attempt were made to secure additional increment of newly induced fractions, depolymerization and/or hydrogen absorption by an extended period of time, as for instance, in excess of in the order of about threehours, the newly induced fractions, depolymerization and/or hydrogen absorption would not be linear functions of the time element.

The overall beneficiated material having newly induced fractions boiling below 200 C.-is stripped, either by gas action or distillation, to an upper limit of 335 C. The stripped'material whose end point is substantially in the order of 335 C. is passed through a high pressure reactor at 465 C. and 200 atm-ospheres pressure while contacting a catalyst chosen from-the group selected from the sixth and eighth` periodic groups. Flow of hydrogen so controlled as to induce a solvent having, as compared to the intermediate starting material, an increased boiling range and solvency. The finally beneficiated material may be fractionated to produce solvents boiling within the range of benzol, toluol, hi-flash naphtha, heavy naphtha andplasticizers. I

In the foregoing examples shown, it will be noted that the present process provides a method for contacting heavyhydrocarbons with hydrogen wherebyto produce a product of lowered solvency, specific gravity and boiling range; stripping from the beneficiated `mass a fraction, as for instance a fraction not including the highest boiling; subjecting said stripped low boiling material, to the controlled action of hydrogen whereby to enhance solvency, said enhanced solvency vflowing from the controlled ac-v tion of hydrogen that, among other things, increases boiling range. v

Looked at in one manner, the present process provides a method for treating aromatic tars, or fractions thereof, with hydrogen .in step-wise manner whereby to producesolvents, said solvents being characterizedby increased solvency, and boiling range when compared to intermediate parent material, as heretoforedisclosed. The said step-wise action of hydrogen is characterized by first providing hydrogen in flow that depolymerizes ring multiplicities thereby, among other things, inducing lowered specific gravity, boiling range and solvency .and second, by providing hydrogen -in flow that increases boiling range and solvency. l

2,291,317 The aforenamed step-wise action of hydrogen' thus provides a method for securing solvents of increased solvency and boiling range from heavy or high boiling hydrocarbons of aromatic content, said high boilers characterized by the presence of ring multiplicities of great thermal susceptibility.

The starting materials of high carbon content, as for instance, high temperature coke-oven tar or fractions thereof, are characterized by, in their raw state, such a percentage of high molecular complexes or polymerized products that the solvents of the present invention, that is to say, solvents of increased boiling range and solvency, are not possible of manufacture therefrom directly in accordance with the present process, but the starting material must first be subjected to the controls of the present process wherein, hydrogen ow, among other things, depolymerizes said molecular complexes.

The depolymerized or partially depolymerized tar or fraction of tar, is then stripped of a percentage of its low boiling ends whereby to provide the intermediate parent material of the solvents of the present process, said intermediate material having increased boiling range and lowered solvency. The residue incidental to said stripping may, because of its depolymerized or partially depolymerized condition serve as recycle material, with or without the addition of other starting material to the end that conversion of the starting material may approach volume for volume of said starting material into solvents of the present invention.

In the conversion of the starting material, partially or approaching unity, into the solvents of the present process, temperatures of as low as 300 C. are usable; pressures as low as 50 atmospheres may be used. However, temperatures and pressures of an increased range provide better commercial practice of the present invention. The time element is desirably that period which affords commercial recoveries of the products of, and incidental to, the present invention.

Concerning gas flow, ows of hydrogen or hydrogen containing gas are usually held in excess of 2,000 cubic feet per barrel material treated. In the step-wise application of hydrogen whereby to provide the solvents of the present invention, a few trials when using any of the starting materials will determine the gas flow, when coordinated with the selected temperature and pressure conditions to effect aforesaid depolymerizing conditions. The gas flow in this instance m-ay be a variable quantity because of the varying qualities of the feed stock and the varying ranges of coordinated temperature and pressure that may be selected. When using any chosen coordination of temperature and pressure, a few trials will readily determine the gas flow that provides depolymerizing conditions to the end that solvency, specic gravity, viscosity and boiling range are lowered.

Concerning the gas flow that increases boiling range and solvency, said flow is held at that point that increases boiling range and solvency thus providing the solvent products of the present invention. A few trials with any of the intermediate starting materials under chosen coordination of temperature and pressure will readily determine the desirable gas flow. For a given coordination of temperature and pressure, the gas ow in the last instance is lower than the gas ow in the rst instance.

' Using some starting materials, a gas flow of from 10,000 to 15,000 cubic feet per barrel, or higher, has proven satisfactory for aforesaid depolymerizing conditions, and vgas flows in the order of 6,000 to 8,000 cubic feet, or lower when increasing solvency and boiling range has proved satisfactory.

By the term benelciated as used herein and in the appended claims, is meant the starting material at least once subjected to the action of hydrogen in accordance with one or more steps of the present invention.

After the starting tar or fraction thereof has been subjected to depolymerizing action as aforestated, the stripping step may be effected at any point selected within a wide range to provide a cut which after further processing is capable of providing substitutes for conventional benzol and/or toluol and/or xylol and/or naphthas, and plasticizers.

Thus the depolymerized starting material may be cut to secure a low boiling product according to the need at hand, said low boiling cut then being subjected to the action of hydrogen that increases solvency and boiling range. The residue from said cut being recycled, if desired, to the end that substantially total conversion of the material remaining liquid be effected.

All catalysts effective in the presence of hydrogen for aforementioned purposes are usable. As for instance, chromium, molybdenum, vanadium, uranium, cobalt, copper and their compounds, for instance, suldes and/or oxides; promoted or not; with or without small amounts of alkali, acid or halid, or derivatives thereof. Small amounts 0f halogen or halogens, as such, or incorporated with other substances; effective catalysts deposited on carriers, as for instance gels, earths, carbon, or the like. In various shapes, as for instance extruded shapes or lengths, pellets, comminuted; mixed with other material possessing desired action or not; with or without other material effecting splitting or not.

When using catalysts, it may be desirable at times to use a comminuted catalyst during the period of the process characterized by depolymerization; thereafter, and during the period characterized by increase in solvency and boiling points to use a rigid catalyst.

By the terms multiplicity of rings, high molecular complexes and polymerized products are meant high boiling fractions of aromatic content, a portion of which at least may be viewed as ring multiples; or, said terms, any or all, may be used to describe high boiling fractions of the starting material, which because of high carbon content are especially susceptible to thermal degradation.

When subjecting high boiling fractions of aforenamed materials to the process of the present invention, it may be desirable prior to the depolymerizing step to at least partially depolymerize the molecular complexes by the use ofa solvent. Said solvent may be added in small amounts, or up to volume for volume, or more, may be used. Refractory solvents are desirable, but others more susceptible to the reactions inherent in and to the present process are usable.

Concerning solvents, it may be said that tar, as for instance high temperature coke oven tar is constituted of high molecular complexes dissolved, cut back or depolymerized with a solvent, said solvent being the lower boiling fractions of said tar.

TheA depolymerizing action of hydrogen,A as aforestated, may be effected in one or more cycles or'chambers, with or without releasing the pressure and with or without variations o-f process controls, including vchanges in either temperature, pressure and/or gas flow; the final action of hydrogen according to the present invention may be effected in one or more cycles or chambers, with or without releasing pressure and with or without variation of process controls, including changes in either temperature, pressure and/or gas flow.

Various modes of practicing the present invention are possible; for instance, the depolymerized starting material may be stripped as for instance by gas movement; the low ends thus stripped may then, with or without releasing pressure, be subjected to the action of hydrogen that increases solvency and boiling point. Or the desired stripped material may be obtained by partial release of pressure which would correspond to the fractional recovery desired or predetermined.

The process may be practiced in a single high pressure chamber, a series thereof, a parallelism thereof, including a multiplicity thereof.

The solvent of the present invention may, as aforestated, be fractionated to provide solvents of various boiling ranges, and in the instance where said solvents are processed from a deep cut on the depolymerized material, the highest boiling fractions thereof serve as especially eflicacious products in the coating industry or the like.

The evaluation of solvent power is conveniently accomplished by finding the well-known aniline point or kauributanol number. The evaluation of plasticizing properties is conveniently accomplished by recourse to methods suggested in chapter VI, The Technology of Solvents, by Dr. Otto Jordon, Mannheim, Germany, translated by Alen D. Whitehead, Chemical Publishing Company of New York, Incorporated, New York, New York.

Minor changes may be made without departing from the spirit of the present invention.

I claim:

l. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen at a temperature and pressure in excess of 300 C. and 50 atmospheres, respectively, for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneficiated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low flow of hydrogen within the limits of about 2000-5000 cubic feet per barrel material treated at a temperature and pressure of at least about 465 C. and 50 atmospheres, respectively, to produce a solvent.

2. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; the process which comprises: subjecting said higher boiling fraction to the action of a relatively high now of hydrogen for a period not in A excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneciated material; increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting the same to the action of a relatively low flow of hydrogen within the limits of about 2000-5000 cubic feet per barrel material treated; and fractionating the last named beneficiated material to segregate a solvent.

3. In the production of a solvent from the refined pitch producing by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a, wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the benefici-ated material; increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low flow of hydrogen within the limits of about 2000-5000 cubic feet per barrel material treated; and fractionating the last n-amed beneciated material to provide a solvent boiling preponderantly between C. and C.

4. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high iiow of hydrogen for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneciated material; and increasing the boiling points of at least a chosen portion of sai-d stripped fractions by subjecting same to the action of a relatively low ow of hydrogen not in excess of about 5000 cubic feet per barrel feed stock, to produce a solvent.

5. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fractions to the action of a relatively high flow of hydrogen at a pressure in excess of about 50 atmospheres and a temperature of at least 400 C. for a period not in excess of about three hours, whereby to avoid polymerization; stripping newly induced fractions from the beneficiated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low iiow of hydrogen within the limits of about 200G-5000 cubic feet per barrel material treated at a temperature and pressure at least'about 465 C. and 50 atmospheres, respectively, to produceasolvent. Y Y

6. In the production of a solvent from the rened pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a Wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen at a temperature and pressure in excess of about 300 C. and about 50 atmospheres, respectively, for a period not in excess of about three hours,

whereby to avoid lowered hydrogen absorption; stripping newly induced fractions from the beneciated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low now of hydrogen within the limits of about 2000-5000 cubic feet per barrel material treated at a temperature and pressure of at least about 465 C. and 50 atmospheres, respec- 10 tively, to produce a solvent.

JACQUELIN E. HARVEY, JR. 

